1. Field of the Invention
The present invention relates to a controller of a power supply and a related method thereof, and particularly to a controller and a related method thereof that can generate jitters in a quasi resonant mode of a power supply.
2. Description of the Prior Art
The switching power supply has been applied to most of consumer electronic devices. The switching power supply can control storing power and releasing power of an inductor through switching of a power switch to provide power matching a specification requirement. However, if switching of the power switch always stays at a specific frequency, the power switch can easily radiate an electromagnetic wave with the specific frequency through transmission lines in the consumer electronic devices, resulting in the switching power supply suffering electromagnetic interference.
In a quasi resonant mode of the switching power supply, the quasi resonant mode can make the power switch of the switching power supply be naturally switched at different valleys to generate similar to natural jitters. However, when the switching power supply operates practically, the power switch of the switching power supply is only usually switched at a fixed valley, resulting in the natural jitters disappearing. Therefore, decrease of electromagnetic interference executed by the quasi resonant mode of the switching power supply is not significant, resulting in the quasi resonant mode of the switching power supply not satisfying a specification for electromagnetic interference.